There are many places online to build a DIY Hoffman apparatus. The ACS offers an electrolysis of water lesson that includes a hand made Hoffman apparatus(link is external) as part of a unit on energy that I used as a resource.
Chad Husting's blog
Looking over my student's papers, there may have been more misconceptions created because of the way I planned the curriculum. In all of the experiments students can see and observe that not all of the crystals or material dissolves yet the water starts to conduct. In their minds there is evidence that they believe either something DOES dissolve or it does NOT. Clearly, partial dissolving is initially too much to consider.
This is a program that has an electronic copy of the map for all teachers to see. The entire map is tied to standards that are a version of state, federal and or local standards. Any formative assessment can easily be graded and tied to a standard. The data can be used to break down how the kids are doing in any one standard and plan future lessons accordingly. If we need to change to meet the needs of our students, we can and should immediately. It is not perfect but is trying to maximize data collection and analysis to help teachers and students.
Show the kids an event. Have them develop a model. Have each kid draw and write about the model and force them to ask themselves if this model can explain the event. As a teacher, first say something nice about it and then look for their misconceptions and use this as a formative assessment. Combine the individual models with others. Slowly build a larger model and constantly ask if this really explains the event.
This is the first isotope activity I have tried where the students can look inside the model that resembled the atom and find information that reinforced what an isotope actually is. Furthermore, the quantitative data forced them to examine beliefs about different types of averages and what the numbers really mean.
Students are told that they have to determine the amount of active ingredient in an antacid tablet. Then I ask them if they have any questions. First it starts with blank stares...then slowly the questions start coming. What exactly is the active ingredient? What does it react with? They are provided information that the active ingredient is baking soda.
Years ago, I took some wonderful material science workshops sponsored by ASM International(link is external). They did an amazing job of helping me add some more tools to my teaching tool kit. Materials are all around us and the workshop was a week long adventure into either creating a material science course or tying material science into existing curriculum. The chemistry of materials can easily be introduced into any curriculum.
Atomsmith works really well on Chromebooks and other platforms. Students can manipulate molecules, add water, do experiments, heat solutions and examine intermolecular forces all on the particulate level. Another nice feature is the "Experiment" section. There are a number of guided activities, usually never more than a page or two. I have found them to be great supplements for activities, experiments and demonstrations.